喷射沉积锭坯的三维成形过程数值模拟与工艺研究
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摘要
使用坐标跟踪法建立了描述喷射成形圆柱坯外形生长的三维数学模型,通过背面剔除和表面三角形单元判断相结合的方法,提出了一种能够准确、简便地计算遮蔽效应的三维算法.该模型严格遵循喷射成形的实际过程建立,经过实验验证,可以对沉积坯外形做出较为准确的预测.基于以上模型,还计算研究了不同工艺参数对锭坯外形演化的影响.模拟结果表明,雾化参数、基板下移速率和初始偏心距是影响沉积坯外形的重要工艺参数.
Spray forming is an advanced technology that is used to produce a variety of highperformance materials with the characteristics of rapid solidification.By properly controlling of spray forming parameters,it is possible to fabricate near-net-shaped preforms,such as rod-billets,strips, and tubes.During the billet spray forming process,the shape of deposit strongly influences the solidification and consequently end-product quality.Therefore,it is necessary to reveal the shape forming mechanism in spray forming process.In the present work,a three-dimensional(3D) model, tracing the coordinates of the moving surface of a growing spray-formed billet,has been formulated to predict the shape evolution of the general deposit.This geometric model takes into account geometrical process parameters in the whole spray forming process:mass flux and mass distribution,position of the atomizer,distance between atomizer and the preform,substrate withdrawal velocity and rotation speed. This makes it possible to model not only the growth of a Gaussian shaped deposit in which case the spray axis and the rotation axis coincide,but also the profile evolution as there is a spray angle between these two axes.For this purpose, "shadowing effect" must be taken into account as a core part of the surface evolution algorithm.On the basis of this 3D model,a timesaving and accurate methodology is established to determine the shadowing effect coefficient,using the "triangular element checking" algorithm coupled with back face culling(BFC).The transient shape modeling has been validated by numerical algorithms and experimental investigation,and has proved that the simulated billet profiles are in good agreement with the experimental data.The effect of spray forming parameters,such as spray distribution parameters,withdrawal velocity,initial eccentric distance,spray angle and angular velocity of rotation,are analyzed.According to the obtained simulation results,the most dominant parameters affecting the shape evolution of deposit are the spray distribution parameters,withdrawal velocity,and initial eccentric distance.It is also found that the spray angle mainly affects the profile of the top transition region of the rod.The effect of the angular velocities of substrate on the shape evolution of the deposit is not significant.Finally,the maximum withdrawal velocity and maximum initial eccentric distance are deduced based on the analysis of shape form mechanism,which can be used to guide the process optimization during spray forming.
Spray forming is an advanced technology that is used to produce a variety of highperformance materials with the characteristics of rapid solidification.By properly controlling of spray forming parameters,it is possible to fabricate near-net-shaped preforms,such as rod-billets,strips, and tubes.During the billet spray forming process,the shape of deposit strongly influences the solidification and consequently end-product quality.Therefore,it is necessary to reveal the shape forming mechanism in spray forming process.In the present work,a three-dimensional(3D) model, tracing the coordinates of the moving surface of a growing spray-formed billet,has been formulated to predict the shape evolution of the general deposit.This geometric model takes into account geometrical process parameters in the whole spray forming process:mass flux and mass distribution,position of the atomizer,distance between atomizer and the preform,substrate withdrawal velocity and rotation speed. This makes it possible to model not only the growth of a Gaussian shaped deposit in which case the spray axis and the rotation axis coincide,but also the profile evolution as there is a spray angle between these two axes.For this purpose, "shadowing effect" must be taken into account as a core part of the surface evolution algorithm.On the basis of this 3D model,a timesaving and accurate methodology is established to determine the shadowing effect coefficient,using the "triangular element checking" algorithm coupled with back face culling(BFC).The transient shape modeling has been validated by numerical algorithms and experimental investigation,and has proved that the simulated billet profiles are in good agreement with the experimental data.The effect of spray forming parameters,such as spray distribution parameters,withdrawal velocity,initial eccentric distance,spray angle and angular velocity of rotation,are analyzed.According to the obtained simulation results,the most dominant parameters affecting the shape evolution of deposit are the spray distribution parameters,withdrawal velocity,and initial eccentric distance.It is also found that the spray angle mainly affects the profile of the top transition region of the rod.The effect of the angular velocities of substrate on the shape evolution of the deposit is not significant.Finally,the maximum withdrawal velocity and maximum initial eccentric distance are deduced based on the analysis of shape form mechanism,which can be used to guide the process optimization during spray forming.
引文
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[4]Zhang J S,Xiong B Q,Cui H.Spray Forming Rapid Solidification Technology Principles and Applications.Beijing:Science Press,2008:1(张济山,熊柏青,崔华.喷射成形快速凝固技术原理与应用.北京:科学出版社,2008:1)
[5]Lavernia E J,Grant N J.Mater Sci Eng,1988;98:381
[6]Singer A R E.Powder Metall,1982;25:195
[7]Lavernia E J,Xu Q.J Jpn Inst Light Met,2000;50:479
[8]FVigaard I A.J Eng Math,1996;30:417
[9]Frigaard I A,Scherzer 0.Siam J Appl Math,1997;57:649
[10]Annavarapu S,Apelian D,Lawley A.Metall Trans,1990;21A:3237
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[13]Lin Y J,Bobrow J E,White D R,Lavernia E J.Metall Mater Trans,2000;31A:2917
[14]Seok H K,Yeo D H,Oh K H,Lee H I,Ra H Y.Metall Mater Trans,1998;29B:699
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[19]Cao F Y,Wu P L,Ning Z L,Zhao W J,Sun J F.Rare Met,2007;26:30
[20]Cui C S,Fritsching U,Schulz A.Metall Mater Trans,2007;38B:333
[21]Choi D S.J Mech Sci Technol,2010;24:1091
[22]Mi J,Grant P S.Acta Mater,2008;56:1588
[23]Cao F Y,Li P J,Fan H B,Cui C S,Li Q C.Mater Sci Technol,2003;11:50(曹福洋,李培杰,范洪波,崔成松,李庆春.材料科学与工艺,2003;11:50)
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[25]Liu D M,Zhao J Z,Ye H Q.Acta Metall Sin,2004;40:873(刘东明,赵九洲,叶恒强.金属学报,2004;40:873)
[26]Fan W J,Zhang Y.J Inner Mongolia Univ Sci Technol,2007;26:203(樊文军,张胤.内蒙古科技大学学报2007;26:203)
[27]Markus S,Cui C,Fritsching U.Mater Sci Eng,2004;A383:166
[28]Mi J,Grant P S,Fritsching U,Belkessam O,Garmendia I,Landaberea A.Mater Sci Eng,2008;A477:2